Microstructure and oxidation resistance of SiC–MoSi2 multi-phase coating for SiC coated C/C composites

In order to improve the anti-oxidation of C/C composites, a SiC–MoSi2 multi-phase coating for SiC coated carbon/carbon composites (C/C) was prepared by low pressure chemical vapor deposition (LPCVD) using methyltrichlorosilane (MTS) as precursor, combined with slurry painting from MoSi2 powder. The phase composition and morphology were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD) methods, and the deposition mechanism was discussed. The isothermal oxidation and thermal shock resistance were investigated in a furnace containing air environment at 1500 °C. The results show that the as-prepared SiC–MoSi2 coating consists of MoSi2 particles as a dispersing phase and CVD–SiC as a continuous phase. The weight loss of the coated samples is 1.51% after oxidation at 1500 °C for 90 h, and 4.79% after 30 thermal cycles between 1500 °C and room temperature. The penetrable cracks and cavities in the coating served as the diffusion channel of oxygen, resulted in the oxidation of C/C composites, and led to the weight loss in oxidation.